1. Field of the Invention
The present invention relates to a cooling apparatus for a water-cooled engine (hereinafter referred to "engine"), and particularly to a cooling apparatus suitable for use in a vehicle.
2. Description of Related Art
In an engine cooling apparatus for a vehicle, for example as described in JP-A-4-257735, with respect to a flow of air entering a vehicle engine compartment from the front side of the engine compartment, a radiator is disposed on the upstream side of the engine.
According to the prior art cooling apparatus described in the publication mentioned above, however, air passing through the radiator directly strikes the engine. Therefore, the engine is cooled by the cold air passing through the radiator in winter season or at times of cold starting, such as immediately after the engine start. Accordingly, there is a problem that it takes a long time to warm up the engine.
Also, because the air passing through the radiator strikes the engine to cool the engine, the temperature of the air having struck the engine is higher than that of the air immediately after the radiator, and some of the air having struck the engine passes around and returns to the upstream side of the radiator through gaps between the inner periphery of the engine compartment and the radiator.
Consequently, the problem arises that because this heated air having struck the engine and passed around to the upstream side of the radiator then passes through the radiator again, the heat-radiation capacity (cooling capacity) of the radiator may be compromised.
Furthermore, according to JP-A-4-257735, a heat exchanger, such as a condenser of a refrigerating cycle, and a radiator are disposed in series with respect to the air flow, and a bypass passage for allowing air to bypass the heat exchanger is formed on the lower side of the heat exchanger.
However, because the bypass passage is provided alongside the heat exchanger, the heat exchanger must inevitably be made small. Accordingly, the heat-radiation capacity of the heat exchanger is compromised, and the pressure inside the heat exchanger rises. Consequently, there is the problem that the compression work of the refrigeration cycle increases.
In addition, because the water-cooled engine is disposed on the downstream side of the radiator, there is also the problem that air having been heated by the radiator is taken in by the engine and consequently the output of the engine is compromised.